The calendar this week contains two of contemporary history’s most somber anniversaries: September 11 and September 13.Two dates, two 24-hour periods ostensibly no different from any other. The sun rises in the morning and sets in the evening, people go about their daily affairs, and life marches on. And yet, both of these days are seared into our individual and collective memories, or at least they should be.For it was on September 11, 2001, when al-Qaida attacked New York and Washington, and on September 13, 1993, when Israel signed the Oslo Accords with the PLO, that the forces of international terrorism claimed two of their biggest triumphs of the modern era.And despite all the differences between them, both events contain a cardinal lesson we dare not forget. It is a cold, hard and uncomfortable truth, one that many would prefer not to grapple with, but which remains a truth nonetheless: there is evil in the world and we must confront it.Many of us recall the morning of 9/11 and the sense of shock that we felt watching the horror unfold before our eyes live on television. The disarray, the chaos, the feeling that this was all coming out of left field. Why, many thought, are these people attacking us all of sudden? But that is only because we have short memories.After all, the 2001 attack was the second time – not the first – that Islamic extremists sought to bring down the World Trade Center. On February 26, 1993, at 12:18 p.m., they set off a truck bomb in the underground parking garage of the North Tower, killing six people and injuring over a thousand.America pursued legal action against the perpetrators, capturing them and putting them on trial. But what if the Clinton administration had taken a more bold approach and launched its own war on terror? What if it had marshaled the vast resources of the US government at the time to move against the growing threat posed by Islamic fundamentalism? Might that not have prevented subsequent tragedies from ever occurring? Five years later, on August 7, 1998, al-Qaida attacked the US embassies in Kenya and Tanzania, killing hundreds of people with truck bombs. Clinton responded by firing a few cruise missiles at targets in Sudan and Afghanistan, but did little else. Osama bin Laden and al-Qaida once again lived to fight another day, and on 9/11 we all saw just how myopic and lethal that decision proved to be.Thousands of innocents lost their lives, and our way of life was changed forever, simply because Washington lacked the will to tackle the cancer before it metastasized.And the same holds true for Israel’s capitulation to Palestinian terror, when prime minister Yitzhak Rabin shook the bloody hand of Yasser Arafat on the White House lawn in 1993.Instead of treating Arafat as the lowly thug that he was, Israel chose to elevate him to the status of lofty statesman, allowing him to create a corrupt and authoritarian entity alongside the Jewish state. Not surprisingly, Arafat and his heirs continued to wage war against Israel, unleashing the greatest wave of terror ever seen in this part of the world. More than 1,000 Israelis were murdered by terrorists in the three years after the signing of Oslo, which was almost twice the number killed in the 25 years that preceded the agreement.And now we find ourselves with a Hamas-run regime in Gaza, rockets occasionally raining down on Israeli cities, and a decrepit and ineffective Palestinian regime in Ramallah that is threatening to declare unilateral independence. Oslo was a classic case of self-deception, one in which Israeli leaders chose to appease the enemy in the vain hope that yesterday’s serial killer would become tomorrow’s friendly neighbor.If Israel had done what was necessary, arresting or killing Arafat for his crimes, rather than allowing him to win a Nobel Prize, who knows how many innocent lives would have been saved? By choosing to accommodate terror rather than eradicate it, the government made a grave and deadly mistake.The lesson, then, of this week’s two anniversaries should be apparent. 9/11 and 9/13 should remind us all that as dangerous as it might be to confront a ruthless enemy, failure to do so is even more perilous.Apathy and appeasement may buy a few years of quiet. But in the end, the price of refusing to respond forcefully to terror is, inevitably, still more terror, and on a much larger scale.The events of 9/11 and 9/13 might never have come to pass had our leadership had the mettle and foresight to recognize this simple truth.We must never forget that evil exists and cannot be negotiated away. There are times when a nation or a civilization comes under assault, and it must arm itself with the courage to fight back.Good will triumph in the end, but only if it is alert to the dangers it faces and responds resolutely.